Concurrent usage of HtmlParser causes infinite loop in HashMap
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Key: TIKA-719
URL: https://issues.apache.org/jira/browse/TIKA-719
Project: Tika
Issue Type: Bug
Components: parser
Affects Versions: 0.9
Environment: SLES 10, JBoss 4.2
Reporter: Christian Goeller
When using Tika in a multithreaded environment I encounter sometimes 2
different types of problems with the HtmlParser
1. NullPointerException in HtmlParser
java.lang.NullPointerException
null
org.ccil.cowan.tagsoup.Element.<init>(Element.java:39)
org.ccil.cowan.tagsoup.Parser.setup(Parser.java:467)
org.ccil.cowan.tagsoup.Parser.parse(Parser.java:439)
org.apache.tika.parser.html.HtmlParser.parse(HtmlParser.java:198)
org.apache.tika.parser.CompositeParser.parse(CompositeParser.java:197)
org.apache.tika.parser.CompositeParser.parse(CompositeParser.java:197)
org.apache.tika.parser.AutoDetectParser.parse(AutoDetectParser.java:135)
org.apache.tika.parser.AutoDetectParser.parse(AutoDetectParser.java:148)
2. infinite loop in HashMap
java.util.HashMap.get(HashMap.java:303)
org.ccil.cowan.tagsoup.Schema.getElementType(Schema.java:122)
org.ccil.cowan.tagsoup.Parser.gi(Parser.java:959)
org.ccil.cowan.tagsoup.HTMLScanner.scan(HTMLScanner.java:505)
org.ccil.cowan.tagsoup.Parser.parse(Parser.java:449)
org.apache.tika.parser.html.HtmlParser.parse(HtmlParser.java:198)
org.apache.tika.parser.CompositeParser.parse(CompositeParser.java:197)
org.apache.tika.parser.CompositeParser.parse(CompositeParser.java:197)
org.apache.tika.parser.AutoDetectParser.parse(AutoDetectParser.java:135)
org.apache.tika.parser.AutoDetectParser.parse(AutoDetectParser.java:148)
Having a closer look at the code of HtmlParser and several tagsoup classes I
assume that the problems comes
from the concurrent usage of a HashMap.
The class org.apache.tika.parser.html.HtmlParser has a static field HTML_SCHEMA.
{code}
/**
* HTML schema singleton used to amortize the heavy instantiation time.
*/
private static final Schema HTML_SCHEMA = new HTMLSchema();
{code}
The class HTMLSchema has a field elementTypes of type HashMap.
{code}
private HashMap theElementTypes = new HashMap(); // String ->
ElementType
{code}
As the HtmlSchema is held static the HashMap is accessed concurrently.
See here for a similar problem:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6423457
Maybe the HTML_SCHEMA should not be static.
Unfortunately the bug cannot be reproduced easily.
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